Two More Random Thoughts

One- a couple days ago, I saw a rug/carpet in a most strange place- in the middle of the road. My question is: if anyone were to trip on either the road and land partway on both, or vice versa, would they get rugburn or road rash?

Two- Why is it that "good morning," "good afternoon," and "good evening" are used as terms of greeting, but "good night" is a farewell?